Summary auto-generated
This study investigated whether hepatitis C virus (HCV) quasispecies populations differ between liver and serum in chronically infected patients. Researchers analyzed the 5' untranslated region (5' UTR) of HCV from paired serum and liver samples from six patients with chronic hepatitis C using strand-specific reverse transcription polymerase chain reaction and single-strand conformation polymorphism analysis. Careful measures were implemented to minimize technical artifacts, including adjusting for template copy number and verifying results through independent replication. In four patients with adequate viral titers, liver samples contained HCV variants not found in serum or in the actively replicating negative-strand RNA fraction. These liver-specific variants differed by 2-17 nucleotides from the dominant 'master' sequence but generally preserved the critical stem-loop secondary structure of the 5' UTR. The authors suggest these liver-specific variants may represent viruses replicating at low levels in hepatic tissues, potentially as an immune evasion strategy or due to adaptation to specific liver cell populations. The study provides evidence that distinct viral populations exist in different anatomical compartments within chronically infected individuals.
Key findings
- Liver tissue contains HCV variants in the 5' UTR region that are absent from serum and replicating virus pools
- Liver-specific variants differ from consensus sequences by 2-17 nucleotide substitutions while preserving critical RNA secondary structures
- HCV negative-strand RNA (replicating virus) shows identical major sequences to serum in patients with adequate viral titers, suggesting compartmentalized low-level replication in the liver
- Careful methodological controls including template copy number adjustment and independent verification are essential to distinguish genuine quasispecies differences from technical artifacts
- The findings suggest functionally distinct viral populations may replicate at different rates in different anatomical compartments
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Abstract
It is unclear whether the sequence populations of hepatitis C virus (HCV) quasispecies in the liver and in serum are different, as a variety of studies on this subject provide conflicting results. In the current study, the populations of HCV 5' untranslated region (5' UTR) sequences in paired serum and liver samples from six patients with chronic hepatitis were analysed. Liver-derived, negative-strand viral RNA was amplified with a highly strand-specific Tth-based assay, and extensive measures, including accounting for template copy number, were undertaken to lower the risk of sporadic artefactual polymorphism. Amplified sequences were compared by single-strand conformation polymorphism analysis and by direct sequencing of identified differences. In four patients, liver samples were found to contain variants within the quasispecies which were not found in serum or negative-strand viral RNA, while in the remaining two patients, low virus titre prevented a reliable quasispecies analysis. These results suggest the presence in the same individual of HCV variants differing in the 5' UTR and possibly replicating with different kinetics.